Machine tool with a linear drive for machining element

ABSTRACT

A machine tool has an operating unit that can be moved by at least one linear motor ( 24 ) along a first guide structure in the direction of a first axis of travel (z-axis) and by at least one second linear motor ( 21, 22 ) jointly with the first guide structure along a second guide structure in the direction of a second axis of travel (y-axis). Each linear motor ( 21, 22, 24 ) includes primary elements as well as secondary elements ( 15/1, 17; 15/2, 17; 23 ). The secondary element(s) ( 23 ) associated with the first axis of travel (z-axis) is/are operatively connected to the operating unit; the secondary element(s) ( 15/1, 17; 15/2, 17 ) associated with the second axis of travel (y-axis) is/are operatively connected to the second guide structure; and the primary elements associated with the different axes of travel (y-axis, z-axis) are operatively connected to the first guide structure and are positioned between the secondary elements ( 23 ) associated with the first axis of travel (z-axis) and the secondary elements ( 15/1, 17; 15/2, 17 ) associated with the second axis of travel (y-axis). The primary elements associated with the different axes of travel (y-axis, z-axis) are arranged in a linear side-by-side array in the direction of one axis of travel (y-axis) while mutually overlapping in the direction of the other axis of travel (z-axis).

BACKGROUND OF THE INVENTION

This invention relates to a machine tool incorporating an operating unitwhich is movable by means of at least one first linear motor along afirst guide structure in the direction of a first axis of travel andalong a second guide structure in the direction of a second axis oftravel by means of at least one second linear motor, jointly with saidfirst guide structure. Each linear motor features a primary element anda secondary element.

A machine tool of this type, model TRUMATIC® HSL 2502 C, is currentlybeing marketed by the Trumpf GmbH & Co., of 71254 Ditzingen, Germany.The functional or operating unit of that machine is in the form of alaser cutting head which, driven by linear motors, moves in a horizontalx-y plane. The first guide structure is a bridge that extends in thex-direction and guides the laser cutting head in the x-direction. Asecond guide structure is provided by the machine frame that carries thebridge with the laser cutting head on support beams and allows thebridge to travel in the y-direction. Linear motors, each with a primaryelement and a secondary element, serve to move the laser cutting head onthe bridge and to move the laser cutting head and bridge assembly alongthe support beams of the machine frame. The secondary motor elementsassociated with the y-axis are attached to the support beams of themachine frame while their matching primary motor elements are attachedto the bridge. Also connected to the bridge is the secondary element ofthe linear motor that drives the laser cutting head in the x-direction.The primary motor element operating in the x-direction is attached tothe laser cutting head.

German Patent A-35 34 214 describes an x-y table encompassing as itsoperating unit a platform that is supported on a base by an intermediatecarriage. Linear motors with primary and secondary elements move theplatform on the intermediate carriage along the y-axis and the platformand carriage combination on the base in the x-direction. The primarymotor elements controlling the movement along the different coordinatesare attached to the top surface of the carriage facing the platform and,respectively, to the bottom surface of the carriage facing the baseopposite the primary elements. Correspondingly, the primary motorelements for the different axes of travel of the platform are verticallyseparated by the body of the intermediate carriage. As a result, theoverall height of that earlier design of an x-y table is ratherconsiderable.

U.S. Pat. No. 6,130,490 discloses an x-y table in which the primaryelements of the linear motors operating in different axes of travel arepositioned in one common plane. That x-y table, however, does notencompass an intermediate structure comparable to the first guidestructure in machine tools of the category here addressed. Moreover, inthat prior art x-y table, the primary motor elements controlling thedifferent axes of travel are positioned at a distance from one anotheralong each axis of travel, resulting in an expansive overall design.

It is the objective of this invention to provide a corresponding machinetool with a compact configuration of a linear motor operated directdrive for at least one operating unit of the machine.

SUMMARY OF THE INVENTION

It has now been found that the foregoing and related objects may bereadily attained in a machine tool with an operating unit that can bemoved by a first linear motor along a first guide structure in thedirection of a first axis of travel (z-axis) and by at least one secondlinear motor jointly with the first guide structure along a second guidestructure in the direction of a second axis of travel (y-axis). Eachlinear motor includes a primary element and a secondary element. Thesecondary elements associated with the first axis of travel (z-axis) areoperatively connected to the operating unit, and the secondary elementsassociated with the second axis of travel (y-axis) are operativelyconnected to the second guide structure. The primary elements associatedwith the different axes of travel (y-axis, z-axis) are operativelyconnected to the first guide structure and are positioned between thesecondary elements associated with the first axis of travel (z-axis),The secondary elements associated with the second axis of travel(y-axis), and the primary elements (19/1, 19/2, 20) associated with thedifferent axes of travel (y-axis, z-axis) are arranged in a linearside-by-side array in the direction of one axis of travel (y-axis) whilemutually overlapping in the direction of the other axis of travel(z-axis).

The side-by-side arrangement makes it possible to position the primaryelements associated with the different axes of travel in a directionperpendicular to the operating plane defined by the axes of travel ofthe operating unit, thus minimizing the system's overall height. Theoverlapping of the primary elements along the respective axis of travelhas a corresponding effect. As an added benefit of the compact design ofthe direct linear drive for the operating unit of machine tools per thisinvention, the mass that must be moved in the operation of the machinetool is minimized. That in turn allows for extraordinarily high travelspeeds of the operating unit without compromising its positionalaccuracy. Machine tools built in accordance with this invention thuspermit precise machining with extremely short processing cycles.

Preferably, the primary elements associated with the different axes oftravel (y-axis, z-axis) overlap in full mutual superposition in thedirection of the first axis of travel (z-axis). As a result, the spacetaken by the primary elements for the different axes of travel isminimized in the direction of the axis of travel in which they overlap.

Desirably, the primary elements associated with the different axes oftravel (y-axis, z-axis) are arranged in a linear side-by-side array inthe direction of the second axis of travel (y-axis) while mutuallyoverlapping in the direction of the first axis of travel (z-axis).

The practicality of this configuration manifests itself by virtue inthat, in the direction of the second axis of travel, it is the primaryelements and, in the direction of the first axis of travel, it is atleast one secondary element, i.e., at least one secondary elementoperatively connected to the operating unit, that are to be moved. Theoperating principle is that the movement of primary elements shouldalways cover the longer travel paths while the movement of secondaryelements should be limited to the shorter travel paths. The dimensionsof the primary elements in the direction of the first axis of travel areparticularly small, and this makes it possible to efficaciously guidethe primary elements in the direction of the second axis of travel bymeans of a second guide structure that is also relatively small in thedirection of the first axis of travel. It follows that the second guidestructure extending in the direction of the second or “long” axis oftravel can be slim in design.

The primary elements associated with the different axes of travel(y-axis, z-axis) mutually overlap in a direction perpendicular to theoperating plane defined by the axes of travel (y-axis, z-axis) of theoperating unit. The primary elements associated with the different axesof travel (y-axis, z-axis) are mutually offset in the directionperpendicular to the operating plane defined by the axes of travel(y-axis, z-axis) of the operating unit, while the primary elementsassociated with an axis of travel (y-axis, z-axis) opposite the otherprimary elements are so positioned as to face the matching secondaryelements.

This geometric offset creates a relatively large distance between theprimary elements controlling one of the axes of travel and the secondaryelements associated with the respective other axis of travel. Thiseliminates possible interference, for instance by eddy currents, thatmight obstruct the movement of the operating unit or the joint movementof the operating unit and a first guide structure along the differentaxes of travel.

The joint movement of the operating unit and the first guide structurein the direction of the second axis of travel (y-axis) is provided by aneven number of multiple linear motors. In the direction of the axis oftravel concerned (y-axis), the primary elements of these linear motorsare evenly distributed on both sides of the primary elements associatedwith the first axis of travel (z-axis).

Thus, the primary elements associated with the second axis of travel aredriven in symmetry with the primary elements for the first axis oftravel.

Each of the primary elements associated with the different axes oftravel (y-axis, z-axis) is provided with a partial housing compartment.These housing compartments together form a modular primary elementhousing which is equipped with at least one common port shared byseveral primary elements and accommodating at least one external powersupply cable, the leads of at least one external monitoring circuit andthe leads of at least one external control circuit.

By positioning the primary elements associated with the different axesof travel in close mutual proximity, they can be jointly accommodated ina common primary element housing. The housing for the primary elementshas at least one common input and/or output port from/to external linesand the number of external primary element input and output cables thattravel along with the movement of the operating unit is reduced to aminimum. The housing compartments that make up the housing for theprimary elements, like the primary elements themselves, may be mutuallypositioned for instance side by side or overlapping in one or severaldirections. Claim 8 describes practical ways in which common connectionscan be provided for the primary elements.

The primary element housing may also accommodate at least one coolantfeed line, and the leads of at least one temperature monitoring circuit.

BRIEF DESCRIPTION OF DRAWINGS

The following specification describes this invention in more detail onthe basis of a design example and with reference to diagrammaticillustrations in which

FIG. 1 is a diagrammatic perspective view of a laser cutting machine inwhich a bridge carries a laser cutting head moved by a direct drivelinear motor system;

FIG. 2 is an enlarged perspective of the components of the linear directdrive system of the machine in FIG. 1;

FIGS. 3 and 4 are front and rear perspective views of the primaryelements of the linear direct drive system in FIGS. 1 and 2;

FIGS. 5 and 6 are two perspective views corresponding to FIGS. 3 and 4with the covers removed to show internal construction;

FIG. 7 is a fragmentary perspective view to an enlarged scale of themachine in FIG. 1 showing the components of the linear direct drivesystem together with the guide structures;

FIG. 8 shows the assembly of FIG. 7 together with the housing of adirectional carriage; and

FIG. 9 is a fragmentary perspective view of the assembly of FIG. 8mounted on the bridge as shown in FIG. 1.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

As indicated in FIG. 1, a machine tool in the form of a laser cuttingmachine 1 encompasses a machine bed 2 with a workpiece support 3 and,flanking it on both sides, longitudinal beams 4. Movably supported onthe beams 4 is a bridge 5 with a laser cutting head 6 which is connectedby a beam guide (not illustrated) to a laser resonator 7 which ismounted on the machine bed 2 and serves to generate a laser beam 8.

A workpiece, in this case a metal plate 9, is placed on the workpiecesupport 3. For the machining process, e.g. for producing contouredcutouts, the laser cutting head 6 moves above it. To do so, the bridge 5can travel along the longitudinal beams 4 of the machine bed 2 in thedirection of a horizontal x-axis. The traversing mechanism in thedirection of the x-axis includes two rack and pinion drives 10 whoseracks 11 are attached to the longitudinal beams 4 and mesh with thepinions driven by electric motors 12 mounted on the bridge 5.

On the bridge 5 a carriage 13, (best seen in FIGS. 8 and 9), supportsthe laser cutting head 6 and is movable in the direction of a horizontaly-axis. The latter extends at a right angle to the x-axis together withwhich it defines a horizontal x-y plane for the movement of the lasercutting head 6.

The laser cutting head 6 proper can be moved on the directional carriage13 along a vertical z-axis. The x-axis, y-axis and z-axis togetherdefine a vertical plane for the movement of the laser cutting head 6.

The directional carriage 13 constitutes a first guide structure alongwhich the laser cutting head 6 can move in the direction of a first axisof travel, that being the z-axis. The bridge 5 serves as a second guidestructure along which the laser cutting head 6, jointly with the firstguide structure (i.e. the directional carriage 13), can be moved in thedirection of a second axis of travel, that being the y-axis. The lasercutting head 6 is the operating unit of the laser cutting machine 1.

The movement of the laser cutting head 6 in its vertical y-z plane isproduced by a linear direct drive system 14, described in detail furtherbelow, whose linear permanent magnet array 15/1, 15/2 on the bridge 5 isschematically outlined in FIG. 1.

As shown in FIG. 2, the linear array 15/1, 15/2 consists of multiplepermanent magnets 16 arranged in a side-by-side configuration in thedirection of the y-axis. Together with a support plate 17, the arrays15/1, 15/2 of permanent magnets 16 constitute secondary elements of aconventional design. The permanent magnets 16 are secured to the bridge5 by the support plate 17. For clarity's sake, only some of thepermanent magnets 16 are depicted in FIG. 2.

Positioned opposite the secondary elements 15/1, 17; 15/2, 17 is aprimary element housing 18 consisting of modular, interconnectedcompartments 18/1, 18/2, 18/3 that house the primary elements 19/1,19/2, 20 (best seen in FIGS. 5 and 6). These are the usual iron coreswith coils. In FIGS. 3 and 4, the framed “active surfaces” of thecompartments 18/1, 18/2, 18/3 are the housing surfaces behind which theprimary elements 19/1, 19/2, 20 are located.

The primary element 19/1, jointly with the secondary element 15/1, 17,makes up a linear motor 21. The primary element 19/2, jointly with thesecondary element 15/2, 17, makes up the linear motor 22. The primaryelement 20, jointly with its associated secondary element 23,constitutes linear motor 24. In the direction of the z-axis thesecondary element 23 includes a linear array of permanent magnets,concealed in the illustrations, as well as a support plate 25. Theprimary elements 19/1, 19/2, 20 are connected to the directionalcarriage 13 by the primary element housing 18.

Both the primary elements 19/1 and 19/2 are rotated by 90° relative tothe primary element 20. It is this orientation of the primary elements19/1, 19/2, 20 and the corresponding orientation of the associatedsecondary elements 15/1, 17; 15/2, 17; 23 which enables the linearmotors 21, 22 to drive the directional carriage 13 with the attachedlaser cutting head 6 in the direction of the y-axis and the linear motor24 can drive the laser cutting head 6 on the directional carriage 13 inthe direction of the z-axis.

In the interest of a compact design of the linear direct drive system14, the primary elements 19/1, 19/2, 20 (i.e. the compartments 18/1,18/2, 18/3 housing them) are positioned side-by-side in the direction ofthe y-axis and fully overlapping in the direction of the z-axis. Theprimary element 20 and the housing compartment 18/3 extend in thedirection of the z-axis over the same distance as the primary elements19/1, 19/2 and the housing compartments 18/1, 18/2.

When the directional carriage 13, with the laser cutting head 6supported by it, is moved on the bridge 5 in the direction of they-axis, the primary element 20 is moved in that same direction by thecorrespondingly aligned secondary elements 15/1, 17; 15/2, 17 that arematched with the primary elements 19/1, 19/2. To prevent this relativemovement of the primary element 20 and secondary elements 15/1, 17;15/2, 17 from generating eddy currents that might interfere with themovement of the directional carriage 13, the primary element 20 isspaced relative to the primary elements 19/1, 19/2, from the secondaryelements 15/1, 17; 15/2, 17 in a direction perpendicular to theoperating plane of the laser cutting head 6 defined by the y-axis andthe z-axis. The primary element 20 and the housing compartment 18/3 and,respectively, the primary elements 19/1, 19/2 and the housingcompartments 18/1, 18/2, are correspondingly offset relative to thesecondary element 23. In this fashion any undesirable interactionbetween the permanent magnets of the secondary element 23 and the ironcores of the primary elements 19/1, 19/2 is prevented.

The primary elements 19/1, 19/2, 20 are supplied and monitored throughthe external electric power supply cables 26, 27, an external coolantfeed line 28, an external coolant discharge line 29 as well as cables30, 31 to external temperature monitoring circuits. To minimize thenumber of lines that must follow the movement of the directionalcarriage 13, the external power supply cable 26 and the cable 30 to theexternal temperature monitoring circuit connect to both the primaryelement 19/1 and the primary element 20. For the same reasons, theexternal coolant feed line 28 and the external coolant discharge line 29carry the coolant for all primary elements 19/1, 19/2, 20. Theconnections to the primary elements 19/1, 20 and, respectively, to theprimary elements 19/1, 19/2, 20 are made by shared ports 32, 33, 34, 35provided on the primary element housing 18. Inside the housing the linesbranch out from the common ports 32, 33, 34, 35 to the primary elements19/1, 19/2, 20.

FIG. 7 depicts the components that guide the laser cutting head 6 on thecarriage 13 in the direction of the z-axis, as well as the componentsthat guide the combination of carriage 13 and laser cutting head 6 onthe bridge 5 in the y-direction. Specifically, these are guide rails 36,37 that are bolted to the directional carriage 13 and guide the linearbearings 38 to which the laser cutting head 6 is attached in thedirection of the z-axis. The laser cutting head 6 is attached to thelinear bearings 38 by a mounting plate, one side of which is bolted tothe laser cutting head 6 while its other side is bolted to the linearbearings 38 and the support plate 25 of the secondary element 23. Guiderails 39, 40 on the bridge 5 serve to guide the linear bearings 41 andthe assembly of carriage 13 and laser cutting head 6 attached to it inthe direction of the y-axis.

The directional carriage 13 is illustrated in detail in FIGS. 8 and 9.As shown, the carriage 13 is designed as a housing that surrounds thelaser cutting head 6 with the secondary element 23 (not illustrated) onfour sides. The dot-dash line in FIG. 8 indicates the axis of the laserbeam 8. With the primary elements 19/1, 19/2 of the linear motors 21, 22positioned in the y-direction on both sides of the primary element 20 ofthe linear motor 24, and with the axis of the laser beam 8 extending atthe level of the center of the primary element 20, the power fed to thelinear motors 21, 22 is applied in symmetrical fashion relative to theaxis of the laser beam 8. This helps maintain a constant, highly precisealignment of the laser beam 8 emanating from the laser cutting head 6and impinging on the metal plate 9.

With the aid of the drive system components described, the laser cuttinghead 6 (i.e. the laser beam emitted by it) can be moved to any desiredspot on the metal plate 9 to be processed. The movement of the lasercutting head 6 in the direction of the z-axis is primarily intended foradjusting the machine to accommodate the thickness of the workpiece tobe cut. Accordingly, the travel path of the laser cutting head 6 in thedirection of the z-axis is substantially shorter than the travel path ofthe combination of carriage 13 and laser cutting head 6 in the directionof the y-axis.

Thus, it can be seen from the foregoing detailed specification andattached drawings that the novel drive assembly is compact and enablesfacile processing of workpieces.

Having thus described the invention, what is claimed is:
 1. In a machinetool with an operating unit (6) that can be moved by at least one firstlinear motor (24) along a first guide structure (13) in the direction ofa first axis of travel (z-axis) and by at least one second linear motor(21, 22) jointly with the first guide structure (13) along a secondguide structure (5) in the direction of a second axis of travel(y-axis), each linear motor (21, 22, 24) including a primary element(19/1, 19/2, 20) as well as a secondary element (15/1, 17; 15/2, 17;23), the improvement wherein (i) the secondary element(s) (23)associated with the first axis of travel (z-axis) is/are operativelyconnected to the operating unit (6); (ii) the secondary element(s)(15/1, 17; 15/2, 17) associated with the second axis of travel (y-axis)is/are operatively connected to the second guide structure (5); (iii)the primary elements (19/1, 19/2, 20) associated with the different axesof travel (y-axis, z-axis) are operatively connected to the first guidestructure and are positioned between the secondary elements (23)associated with the first axis of travel (z-axis) and the secondaryelements (15/1, 17; 15/2, 17) associated with the second axis of travel(y-axis); (iv) the primary elements (19/1, 19/2, 20) associated with thedifferent axes of travel (y-axis, z-axis) are arranged in a linearside-by-side array in the direction of one axis of travel (y-axis) whilemutually overlapping in the direction of the other axis of travel(z-axis); and (v) said primary elements (19/1, 19/2, 20) associated withthe different axes of travel (y-axis, z-axis) are mutually offset andmutually overlapping in the direction perpendicular to the operatingplane defined by the axes of travel (y-axis, z-axis) of the operatingunit (6), while the primary element(s) (19/1, 19/2, 20) associated withan axis of travel (y-axis, z-axis) opposite the other primary element(s)(19/1, 19/2, 20) is/are positioned towards the matching secondaryelements (15/1, 17;, 15/2, 17; 23).
 2. The machine tool in accordancewith claim 1 wherein the primary elements 19/1, 19/2, 20) associatedwith the different axes of travel (y-axis, z-axis) overlap in fullmutual superposition in the direction of said first axis of travel(z-axis).
 3. The machine tool in accordance with claim 1 wherein theprimary elements (19/1, 19/2, 20) associated with the different axes oftravel (y-axis, z-axis) are arranged in a linear side-by-side array inthe direction of the second axis of travel (y-axis) while mutuallyoverlapping in the direction of the first axis of travel (z-axis). 4.The machine tool in accordance with claim 1 wherein the joint movementof the operating unit (6) and the first guide structure (13) in thedirection of the second axis of travel (y-axis) an even number ofmultiple linear motors (21, 22) is provided and that in the direction ofthe axis of travel concerned (y-axis), the primary elements (19/1, 19/2)of these linear motors (21, 22) are evenly distributed on both sides ofthe primary element(s) (20) associated with the first axis of travel(z-axis).
 5. The machine tool in accordance with claim 1 wherein each ofthe primary elements (19/1, 19/2, 20) associated with the different axesof travel (y-axis, z-axis) is provided with a partial housingcompartment (18/1, 18/2, 18/3) and that together these housingcompartments form a modular primary element housing (18) is equippedwith at least one common port (32, 33, 34, 35) shared by several primaryelements (19/1, 19/2, 20) and accommodating at least one external powersupply cable, the leads of at least one external monitoring circuit andthe leads of at least one external control circuit.
 6. The machine toolin accordance with claim 1 wherein a primary element housing (18) isequipped with at least one common port (32, 33, 34, 35) shared byseveral primary elements (19/1, 19/2, 20) and accommodating at least oneof the components selected from the group consisting of at least onepower supply cable (26), at least one coolant feed line (28), and theleads of at least one temperature monitoring circuit (30).
 7. Themachine tool in accordance with claim 1 wherein said machine tool is alaser cutting machine with a laser cutting head as the operating unit(6).